Quadruple Saturn Moon Transit Snapped by Hubble

PASADENA, Calif. -- On Feb. 24, 2009, NASA's Hubble Space
Telescope took a photo of four moons of Saturn passing in front
of their parent planet. The pictures were taken by the Wide
Field and Planetary Camera 2, developed and built by NASA's
Jet Propulsion Laboratory, Pasadena, Calif.

In the new view, the giant orange moon Titan casts a large
shadow onto Saturn's north polar hood. Below Titan, near the
ring plane and to the left, is the moon Mimas, casting a much
smaller shadow onto Saturn's equatorial cloud tops. Farther
to the left, and off Saturn's disk, are the bright moons Dione
and the fainter Enceladus.

These rare moon transits only happen when the tilt of Saturn's
ring plane is nearly "edge on" as seen from Earth. Saturn's rings
will be perfectly edge on to our line of sight on Aug. 10, 2009,
and Sept. 4, 2009. Unfortunately, Saturn will be too close to the
sun to be seen by viewers on Earth at that time. This "ring plane
crossing" occurs every 14 to 15 years. In 1995 to 1996, Hubble
witnessed the ring plane crossing event as well as many moon transits,
and even helped discover several new moons of Saturn.

The banded structure in Saturn's atmosphere is similar to Jupiter's.

Early 2009 was a favorable time for viewers with small telescopes to
watch moon and shadow transits crossing the face of Saturn. Titan,
Saturn's largest moon, crossed Saturn on four separate occasions:
January 24, February 9, February 24, and March 12, although not all
events were visible from all locations on Earth.

These pictures were taken with the Wide Field and Planetary Camera 2 on
Feb. 24, 2009, when Saturn was roughly 1.25 billion kilometers (775 million miles)
from Earth. Hubble can see details as small as 300 kilometers (190 miles)
across on Saturn. The dark band running across the face of the planet
slightly above the rings is the shadow of the rings cast on the planet.